Bug#453749: Fix serial console detection on ia64
Package: finish-install
Version: 2.13
Severity: important
Tags: patch
If you boot an ia64 system[1] without specifying a console= parameter,
the kernel will try to map /dev/console to whatever settings were
detected from EFI (firmware interface). If EFI uses a serial console,
/dev/console will be mapped to that same serial device.
d-i interacts with the user via /dev/console, so most of the time the
installer doesn't really care what the underlying device is. That is,
until the system needs to decide where it should run gettys, and where
root logins are permitted. This works is done by 90console.
90console attempts to detect the real console device by dereferencing
/proc/<di-pid>/fd/0. If a system was booted w/ console=ttyS0,
/proc/<di-pid>/fd/0 will link to /dev/ttyS0.
However, on certain ia64 platforms[2], this link points to the
ever-so-helpful /dev/console. The only way we've found to identify the
correct device is to use a small C program that issues an ioctl to the
device to retrieve the line number and speed (thanks to Bryan
Stillwell for this research/work[3]).
The workaround for this in etch is to always specify a console=
parameter, thereby disabling the automatic console setup.
The attached patch to di-utils adds a slightly modified version of Bryan's
utility. This utility was originally called getserialdev - I've
renamed it to serial-console-info, since I think it better describes
the function. Also, getserialdev's output was of the form:
# ./getserialdev
ttyS2 115200
I've modified this to instead tag the data, so that it should be
easier to maintain backwards compatability should this utility provide
additional output in the future. e.g.:
# ./serial-console-info
DEV=ttyS2
SPEED=115200
The attached patch to finish-install adds support for using
serial-console-info, if available, to 90console. Processing behaves
just as before, until it finds that /proc/<di-pid>/fd/0 is pointing at
/dev/console. It will only then run serial-console-info to see if it
can determine that /dev/console is actually a serial device.
I briefly considered implementing serial console detection entirely
with serial-console-info - but decided against it. The major problem
is that serial-console-info assumes that any device it finds has a
ttyS prefix, which may not always be correct.
[1] Possibly other EFI-based systems as well, I haven't verified
[2] an rx1600 w/ an MP for one
[3] https://launchpad.net/bugs/48752
--
dann frazier
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